1. Field of the Invention
The invention relates to optical communication equipment and, more specifically, to micro-electromechanical devices for use in such equipment.
2. Description of the Related Art
Optical communication equipment often employs micro-electromechanical systems (MEMS). A typical MEMS system may include an array of micro-machined mirrors, each mirror individually movable in response to an electrical signal. Such an array may be employed in an optical cross-connect, in which each mirror in the array receives a different beam of light, for example, from an input optical fiber. The beam is reflected from the mirror and can be redirected to a different location, e.g., at which is located an output optical fiber. The particular output fiber may be selected by rotating the mirror. More details on the principle of operation and methods of manufacture of MEMS devices having mirror arrays may be found, for example, in commonly assigned U.S. Pat. No. 6,201,631, the teachings of which are incorporated herein by reference.
One problem with prior art MEMS devices having relatively large (e.g., about 100 xcexcm in length) mirrors is that the spacing between the mirror and the corresponding actuating electrode(s) has to be relatively large to achieve relatively large (e.g., about 10xc2x0) rotation angles, However, increasing the spacing leads to a corresponding increase in the voltage that has to be applied to the electrodes to rotate the mirror. As appreciated by those skilled in the art, it is often undesirable and/or impractical to have MEMS devices whose operating voltages exceed about 100 V.
Problems in the prior art are addressed, in accordance with the principles of the present invention, by a MEMS device having a movable mirror and a movable actuator plate mechanically coupled together such that a relatively small displacement of the plate results in mirror rotation by a relatively large angle.
In a representative embodiment, the mirror and actuator plate are supported on a substrate. The actuator plate moves in response to a voltage difference applied between (a) an electrode located on the substrate beneath the plate and (b) the plate itself. One or more springs attached to the plate provide a counteracting restoring force when they are stretched from their rest positions by the plate motion. The mirror has a handle portion configured as a lever arm. A spring attached between the actuator plate and the handle portion transfers the motion of the actuator plate to the mirror such that, when the actuator plate moves toward the substrate, the spring pulls the handle portion to move the mirror away from the substrate. Advantageously, relatively large mirror rotation angles may be achieved using relatively low actuator voltages. For example, a mirror that is about 100 xcexcm in length may be rotated by an angle of about 15 degrees using an actuator voltage of only about 50 V.
In another representative embodiment of the invention, a MEMS device has first and second plates, each supported on, and positioned offset from, a substrate. The second plate is rotatably connected to the substrate. The connection defines a rotation axis and first and second portions of the second plate including its opposite ends with respect to the rotation axis. One end of the first plate is movably connected to the first portion of the second plate, while the other end of the first plate is connected to the substrate.